XQuery

Namespaces

Namespaces are used to identify the vocabulary to which XML elements and attributes belong, and to disambiguate names from different vocabularies. This section provides a brief overview of the use of namespaces in XQuery for those who expect to be writing queries with basic use of namespaces. More detailed coverage of namespaces, including a complete explanation of the use of namespaces in XML documents, can be found in Chapter 10.

Many of the names used in a query are namespace-qualified, including those of:

• Elements and attributes from an input document

• Elements and attributes in the query results

• Functions, variables, and types

Example 2-3 shows an input document that contains a namespace declaration, a special attribute whose name starts with xmlns. The prod prefix is mapped to the namespace http://datypic.com/prod. This means that any element or attribute name in the document that is prefixed with prod is in that namespace.

Example 2-3. Input document with namespaces (prod_ns.xml)

<prod:product xmlns:prod="http://datypic.com/prod">
  <prod:number>563</prod:number>
  <prod:name language="en">Floppy Sun Hat</prod:name>
</prod:product>

Example 2-4 shows a query (and its results) that might be used to select the products from the input document.

Example 2-4. Querying with namespaces

Query
declare namespace prod = "http://datypic.com/prod";
for $product in doc("prod_ns.xml")/prod:product
return $product/prod:name
Results <prod:name xmlns:prod="http://datypic.com/prod" language="en">Floppy ...